New software called iTweezers lets scientists drag molecules
around the screen as easily as shooting angry birds at pigs.

"It's cool because it takes something that normally lives on a
lab bench, and makes it so simple," said physicist Richard Bowman
of Scotland's University of Glasgow, lead author of a paper in the
4 March Journal of Optics describing the new software. "We
have visitors who have never seen an optical tweezer before in
their lives, and they happily move particles around."

'You can learn stuff by physically connecting in a different
way.'

The new app is an interface for controlling optical tweezers, an instrument that uses
laser light to trap and move microscopic objects. It works a little
like a sci-fi tractor beam: The radiation from a tightly focused
beam of light applies enough pressure to tiny objects like cells or
proteins to pin them to the spot or push them around.

The invention of optical tweezers won Secretary of Energy Steven
Chu a Nobel Prize in Physics, and they have proven
their worth in biology labs, where they have been used to trap and
manipulate everything from viruses to DNA. They have helped measure
some of the smallest forces ever recorded, detected how DNA's double helix unzips, and watched molecular motors move
matter around inside cells.

But most of the early experiments with optical tweezers could
only focus on one spot at a time.

"Up till now, people typically controlled things using a mouse,"
said physicist Gordon Love of Durham University in England,
who was not involved in the new work. "A mouse is great for moving
around one thing like a cursor on a screen, but it's no good for
moving around multiple things."

The multitouch interface was born when Bowman's colleagues at
England's University of Bristol struggled to control a
tiny rod about 300 nanometers wide. To keep the rod from flipping
over, the physicists needed to pin the rod down in several places
at once.

In 2009, the team built a custom table that let them drag and drop
microscopic glass beads just by swiping their fingers along a layer
of paper coated with silicon rubber. The device was clunky and
complicated, but it mostly worked.

But soon the team found a more elegant setup: the iPad.

"When the iPad came out we thought, well hey, this is just like
the big table, except it's small and works really well," Bowman
said.